Wastewater from municipal sewage systems, large-scale agricultural operations, and industrial waste product systems often includes large amounts of organic and inorganic waste material that, if left untreated, can create severe odors due to anaerobic decay and can generate toxic products. Treating such waste generally involves collecting the organic and inorganic waste material in a stream of liquid or water, and collecting the waste in settling pools, ponds, or lagoons. Thereafter, the waste is allowed to settle in progressive settling ponds, pools, or lagoons, and any floating detritus is allowed to decompose, allowing the effluent to be run off relatively free of the debris for further treatment or clarification. During this process, the addition of oxygen sufficient to meet the basic oxygen demand is preferred so that the waste material in the water will undergo biodegradation that converts the wastewater into a relatively nontoxic, non-offensive effluent. Since anaerobic decomposition is inefficient as compared to aerobic decomposition, and anaerobic decomposition often results in the production of a malodorous sulfur-containing gas, it is preferred to add oxygen to the wastewater to increase decomposition while reducing or eliminating the existence of anaerobic decomposition. Various approaches have been used, typically by surface aeration or by submerged aeration systems wherein air is pumped below the surface of the water, or sometimes by a rotating impeller that mixes the wastewater and entrains air into that water. While each of these previous designs may have application in that have been considered and developed, there is still a need for an improved apparatus for economically mixing a large quantity of wastewater with sufficient air to at least satisfy the basic oxygen demand of the wastewater to promote biodegradation of the waste materials, and/or to reduce or eliminate offgassing of offensive odors.